In Access, difference b/w primary key and index?

Answer 1 is totally incorrect. Please go to learn more about DBMS topic first.
In academic aspect, the definition of primary key should be as following.
a unique key is field(s) identifing a record in a table. Primary key is one of unique key(s) of a table.
The index in access is used for making query a table faster. just like the index at the end of a book.
To be primary key, the database usually will form an index on the fields.

2008-05-28 19:15:41 補充：
primary key does not nessary to connect tables. instead key formed for the relationship between the tables is foriegn key. It makes use for maintainening the consistancy of the tables.

A table can only have ONE primary key but can have more than one index.

A primary key must contain unique (non-repeating) values. An index can be set up to allow duplicate values or only unique values.

A primary key is also an index.

Primary Key is connecting two table and unique
eg A table : One subject's Primary Key is ID number 28
B table : FK must have ID number 28 and other information is about A table(/ID number 28)

Indexed is about the value
eg "Name" <<< The value is about lenght or format(ChanTaiMan / chan tai man etc.)

希望幫到你啦 ^^